1 files changed, 20 insertions, 8 deletions

diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 3ab43df089cd..dbc81acb7e93 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -30,26 +30,38 @@
 /*
  * IDT vectors usable for external interrupt sources start
  * at 0x20:
+ * hpa said we can start from 0x1f.
+ *   0x1f is documented as reserved.  However, the ability for the APIC
+ *   to generate vectors starting at 0x10 is documented, as is the
+ *   ability for the CPU to receive any vector number as an interrupt.
+ *   0x1f is used for IRQ_MOVE_CLEANUP_VECTOR since that vector needs
+ *   an entire privilege level (16 vectors) all by itself at a higher
+ *   priority than any actual device vector.  Thus, by placing it in the
+ *   otherwise-unusable 0x10 privilege level, we avoid wasting a full
+ *   16-vector block.
  */
-#define FIRST_EXTERNAL_VECTOR           0x20
+#define FIRST_EXTERNAL_VECTOR           0x1f
 
+#define IA32_SYSCALL_VECTOR             0x80
 #ifdef CONFIG_X86_32
 # define SYSCALL_VECTOR                 0x80
-# define IA32_SYSCALL_VECTOR            0x80
-#else
-# define IA32_SYSCALL_VECTOR            0x80
 #endif
 
 /*
- * Reserve the lowest usable priority level 0x20 - 0x2f for triggering
+ * Reserve the lowest usable priority level 0x10 - 0x1f for triggering
  * cleanup after irq migration.
+ * this overlaps with the reserved range for cpu exceptions so this
+ * will need to be changed to 0x20 - 0x2f if the last cpu exception is
+ * ever allocated.
  */
+
 #define IRQ_MOVE_CLEANUP_VECTOR         FIRST_EXTERNAL_VECTOR
 
 /*
- * Vectors 0x30-0x3f are used for ISA interrupts.
+ * Vectors 0x20-0x2f are used for ISA interrupts.
+ *   round up to the next 16-vector boundary
  */
-#define IRQ0_VECTOR                     (FIRST_EXTERNAL_VECTOR + 0x10)
+#define IRQ0_VECTOR                     ((FIRST_EXTERNAL_VECTOR + 16) & ~15)
 
 #define IRQ1_VECTOR                     (IRQ0_VECTOR +  1)
 #define IRQ2_VECTOR                     (IRQ0_VECTOR +  2)
@@ -122,7 +134,7 @@
 
 /*
  * First APIC vector available to drivers: (vectors 0x30-0xee) we
- * start at 0x31(0x41) to spread out vectors evenly between priority
+ * start at 0x31 to spread out vectors evenly between priority
  * levels. (0x80 is the syscall vector)
  */
 #define FIRST_DEVICE_VECTOR             (IRQ15_VECTOR + 2)